Spooncraft

Bornakk answered that very question today on the forums. The question being ” What exactly does it effect? I can see dodge in the one stat, but is that it?”. Expertise is something that a lot of theorycrafters are saying is a very powerful tanking stat and should be valued over +hit rating. 

It reduces the chance for a players’s melee attacks to be dodged or parried. (src) 

So why is it more viable for a tank instead of DPS? I mean DPS like rogues and enhance shaman and DPS warriors need to not have their attacks dodged or parried right? Actually if you’re melee DPS then you should be BEHIND the boss almost 100% of the time barring it having a tail and doing a tail swipe, so parries shouldn’t factor into your compensation and unless it’s Moroes or some other heavy dodge boss then that too shouldn’t be such a big hindrance to DPS.

Stats that should be focussed on more would be attack power, crit, hit, and even to a lesser degree armor penetration (mainly for rogues and hunters far as I can tell)  and as for PVP I can see how it is very tempting but as before, in PVP people take most damage not from regular strikes but while they are locked down in some way or from magic damage which is unaffected by expertise.